Question

Write a method that concatenates two strings passed as parameters.
   Version #1 - assign to the 1st parameter the concatenation of both parameters.
Perform the concatenation using the + operator.
We are assuming reference parameter work that way (they don't).
   Version #2 - fine. return the value of the 1st param after concatenating
to it the second parameter then.
   Version #3 - Let's do it the proper way now, I say.
Create a temporary String reference variable in your method.
Assign to it the result of concatenating both parameters.
Return the temporary variable.
   Please note, this exercise is only useful if you take the time to trace or draw
   a stack diagram to make sure you exactly understand why each version works or
   does not work (and how they do so). Office hours are a good place to get help
   if you are rusty with tracing or stack diagrams.
*/
public class TinkeringWithStringsLive {
   public static void main(String[] args){
String s1 = "hello";
String s2 = "world";

version1(s1,s2);
System.out.println(s1);
System.out.println(version2(s1,s2));
System.out.println(version3(s1,s2));
   } // end main
  
   public static void version1(String s1, String s2){
// please note that the return type is void
// we modify s1 instead of returning anything
// worth a try, right?
   }// end method version1
  
   public static String version2(String s1, String s2){

return "";
   }// end method version2
  
   public static String version3(String s1, String s2){

return "";
   }// end method version3
} // end class

Answer 1

public class TinkeringWithStringsLive {
        public static void main(String[] args) {
                String s1 = "hello";
                String s2 = "world";

                version1(s1, s2);
                System.out.println(s1);
                System.out.println(version2(s1, s2));
                System.out.println(version3(s1, s2));
        } // end main

        public static void version1(String s1, String s2) {
                // Return is void, hence we are not returning anything
                s1 = s1 + s2;
                
                // When values are passed to the method, they are given as a copy of original value
                // Hence s1 and s2 are copies inside method.
                // If we change s1 in the method, it is not going to affect anything outside the method
        }// end method version1

        public static String version2(String s1, String s2) {
                s1 = s1 + s2;
                
                // Here, we change the string s1 inside the method and then return the modified string.
                // the returned string is captured in main method and shown there, hence we see the change.
                return s1;
        }// end method version2

        public static String version3(String s1, String s2) {
                String temp = s1 + s2;
                
                // We just created another string inside the method which is concatenated, and we are returning
                // that. main method captures and shows it.
                return temp;
        }// end method version3
} // end class

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